Text Comprehension is an important means of knowledge acquisition in almost all domains. The ability to process complex, written information is essential if individuals are to make informed decisions regarding their physical, emotional, and financial well being. Reading involves complex interactions between reader-related factors (e.g., word-decoding skill, background knowledge) and text-related properties (e.g., syntactic complexity, coherence). The goal of this study is to understand how reader characteristics and text properties combine to influence reading processes and comprehension performance. We capitalize on recent advances in psychometrics, involving multilevel modeling, to examine reader and text interactions in a more sophisticated manner than has been possible before. In this study, reading time is decomposed to reveal the subcomponent processes of comprehension. Properties of words, sentences, and texts are used to predict reading-specifically, young adults'eye movements and fixations. The relations between specific text properties and reading are then used as criterion variables in second-level analyses to determine how they are influenced by a large number of reader characteristics (e.g., word-decoding ability, working-memory (WM) capacity). One aim of this proposal is to investigate two closely related, theoretical issues. First, what accounts for the covariation between performance on WM tasks and sentence understanding? We compare models in which the covariation is due to individual differences in WM capacity and models in which the covariation is due to individual differences in language skill and experience. Second, what is the nature of reading skill? We compare models in which differences in skill are due to variation in a single mechanism (e.g., word-decoding ability) and models in which differences are due to variation in multiple mechanisms- language specific mechanisms, such as word-decoding skill, and general cognitive mechanisms, such as WM capacity, This project is relevant to public health in its potential to improve the comprehensibility of written health information. Comprehension is facilitated to the extent that the properties of the text match the skills of the reader. This project can contribute to the development of guidelines for text revision that will improve comprehension in heterogeneous groups of readers.